Power system with computer-controlled fuel system

ABSTRACT

The present invention is a fuel-control system for a turbine which includes a programmable logic controller. The controller manages utility and stored natural gas sources using a surge tank and pressure-control valve arrangement and is backed up by a hydrogen-powered fuel cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

FIELD OF THE INVENTION

In general, this invention is a control system for a power-producingfacility. More specifically, the invention relates to the field of usingcontrol systems to maintain the delivery of gas fuel to a turbine. Theinvention also relates to the field of providing backup power to acontroller which exists in a power-system environment.

BACKGROUND OF THE INVENTION

Conventional power systems for telecommunications facilities have usedAC which is purchased from a commercial utility. Because of blackoutsand other disturbances in the commercial power grid, some facilities usea diesel generator to back up the commercial AC. When the AC power goesdead, the diesel generator is activated. It takes a while for thegenerator to come online, however. In the interim, an array of batterieswill bridge the downtime. If the diesel generator fails, e.g., runs outof fuel, the batteries will drain to power the facility until they runout.

Gas turbines have been widely used by utility companies to generateelectrical power. Many are adapted such that they operate on naturalgas. Such turbines are normally included in an arrangement which ensuresthat the natural gas fuel is delivered at a steady pressure. Thisprevents erratic electrical production.

SUMMARY OF THE INVENTION

The present invention is a fuel-control system for a gas-consumingdevice. The system includes a controller (e.g., a programmable logiccontroller). The controller is used within an environment in which afirst source of a first gas is received through a first conduit whichleads into a chamber. There is also a first pressure-control valve and afirst sensor in the first conduit. The first sensor takes a first-sensorreading regarding a first pressure. This reading is transmitted to thecontroller.

The system also includes a second source of a second gas derived from astorage container through a second conduit into the chamber. A secondpressure-control valve is located in the second conduit along with asecond sensor. The second sensor also takes readings which aretransmitted to the controller.

The controller uses readings from the first and second sensors tomanipulate the first and second pressure-control valves to maintain asteady pressure level in a third conduit which runs from the chamber tothe gas-consuming device.

In another embodiment, the third conduit also has a sensor and apressure-control valve to assist in maintaining steady gas pressure sothat the turbine is able to run smoothly.

The system also includes an electrical power backup system for thecontroller. This system uses the output from a fuel cell to power thecontroller in the event the turbine fails (e.g., runs out of fuel).

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in detail below with reference to theattached drawing figures, wherein:

FIG. 1 is a schematic diagram showing the power system of the presentinvention.

FIG. 2 depicts the fuel-control system of the present invention.

FIG. 3 shows the several components of the invention which are containedin a control cabinet.

FIG. 4 is a flow diagram showing the processes of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The system disclosed herein uses a gas turbine generator as the primarysource of power to sustain DC power to a DC bus which is electricallyconnected to a base transceiver station (BTS). The turbine normallyoperates on natural gas from a utility pipeline, but if the utilitysource is unavailable (e.g., a backhoe ruptures a pipeline) or thepressure has dropped below what is necessary to drive the turbine, thesystem can call on a backup source of natural gas which is stored intanks. The turbine is able to run on only utility natural gas, partialutility and partial stored natural gas, or only stored natural gasthanks to a valve arrangement using pressure-controlled valves and asurge tank. The pressure-controlled valves are controlled using acontroller. The controller may be some kind of computing device, e.g., aprogrammable logic controller (PLC) or a microprocessor. A PLC is usedin the preferred embodiment. This arrangement makes for smoothtransitioning between utility and stored natural gas sources.

Lithium Metal Polymer batteries (LMPs) are connected into the DC bus.The LMPs are always online. When the electrical output of the turbinegenerator dips, the LMPs will cover the dip so that the BTS does notexperience any temporary power drop. When the turbine is inactive, theLMPs drain to back up the BTS.

Should the LMPs completely lose their charge to the point that the BTSpower requirements are not met, the system includes a low-power fuelcell which is used to back up the PLC only. When the fuel cell isbrought online, the PLC circuit is isolated from the DC bus by throwinga breaker. Because it is backed up with the fuel cell, the PLC remainsfunctional and is able to continue to control the valves even though theDC bus is dead. It also enables the PLC to continue to transmit alarmmessages so that interested parties are able to monitor what ishappening at the site.

FIGS. 1-4 help in understanding the disclosed embodiment. Referringfirst to FIG. 1, a schematic diagram 100 shows the many components of apower system which relies primarily on a microturbine generator 104which is backed up by one or more LMP batteries 106. This backuparrangement is used to ensure that DC power is maintained to thepower-distribution unit (not shown) for a BTS 102. The BTS is theradio-hardware portion of a cellular base station. It is involved in thetransmission and receiving of voice and data. Power distribution unitscomprise the electrical equipment for making the necessary connectionsinto the telecommunication-cell-site equipment.

Microturbine generator 104 produces AC. BTS 102 consumes DC, not AC.Thus, the AC received from microturbine generator 104 must be converted.To do this, system 100 includes one or more rectifiers 134. Rectifiers134 convert AC to DC. The particular rectifiers used in the presentinvention are switch mode rectifiers (SMRs). SMRs are advantageous foruse here because they are highly efficient, small, and relatively lightweight.

The DC output from the rectifiers 134 is electrically connected into aDC bus 130. The DC input to BTS 102 is also connected to bus 130. Thus,BTS 102 is able to receive its primary source of power from turbine 104.

If the turbine fails for some reason, e.g., for lack of fuel, the LMPs106 will immediately pick up the load because they are also connectedinto bus 130. This connection also causes them to be charged when theturbine is functional. The LMPs used in the preferred embodiment of theinvention are 48-volt, 63-amp-hour batteries manufactured by Avestor,Inc. (Model No. SE 48S63), but the scope of the invention is not to belimited to any particular battery, manufacturer, or amp-hour/voltagelevel used. Other kinds of batteries could be used instead and stillfall within the scope of the present invention. Three batteries are usedin the present embodiment.

FIG. 1 also discloses a control system 108 which includes a controller110 which is, in the preferred embodiment, some form of computingdevice. Controller 110 serves numerous purposes. First, it is used tosend alarm information to an outside monitoring administrator whencertain conditions are sensed. Sensors at different points will transmitalarm messages if certain events occur. For example, pressure sensorswill indicate disruption in availability of utility natural gas, storednatural gas, and stored hydrogen (which is used to fuel a PLC backupfuel cell). A pressure sensor will also be used to sense disruption inthe feeder line to the turbine. Other alarms will be transmitted in theevent of electrical irregularities. Properly located voltage sensorswill indicate voltage drops at the turbine, LMP, and fuel-cell outputs.These alarms will be transmitted to an interested party. This enablesremote monitoring by an administrator not at the site.

Second, controller 110 regulates the delivery of natural gas to turbine104 and enables the automated administration of utility versus storedsources with preference given to natural gas from the utility. This isdone using a valve arrangement which is responsive to measurements takenby a plurality of pressure sensors.

Third, the controller is adapted to open and shut a breaker 140 toisolate the control system from the DC bus upon the occurrence ofcertain conditions as will be discussed in more detail later.

PLCs like the one used in the preferred embodiment as controller 110will be known to those skilled in the art as devices which are widelyused for industrial control applications. They employ the hardwarearchitecture of a computer but also include a relay control subsystem. APLC uses these components to automatically respond to sensed conditionsin the power system. Though a PLC is used in the preferred embodiment,another kind of device, such as microprocessor arrangements could beused instead, and other computing devices could also be used and stillfall within the scope of the present invention.

Controller 110 is supported by an independent backup system. The backupsystem includes a fuel cell 112 which is driven using gaseous hydrogenfuel from a hydrogen tank 114.

Fuel cells are electrochemical-energy-conversion devices. They utilizehydrogen and oxygen. Proton exchange membranes (or other equivalentdevices) in the fuel cell cause the electron from hydrogen to be removedtemporarily. Later, this hydrogen electron is returned when the hydrogenis combined with the oxygen to produce water. This creates electricity.The reaction is entirely noncombustive and generates DC electricalpower. Because the only by-products of this reaction are heat, water,and electricity, a fuel cell is friendly to the environment. Inaddition, a fuel cell is capable of providing electrical power for aslong as hydrogen fuel is supplied to the unit. It does not dischargeover time like a battery.

In the preferred embodiment disclosed in FIG. 1, fuel cell 112 includesa plurality of PEMs. Though fuel cell 112 used in the preferredembodiment uses PEMs, other fuel-cell technologies exist which might beused instead and still fall within the scope of the present invention.One example of a PEM-type fuel cell which is suitable for use with thepresent invention is a 500W modular, cartridge-based, proton exchangemembrane power module manufactured by ReliOn, Inc. of Spokane, Wash.

In the FIG. 1 arrangement, fuel cell 112 receives hydrogen fuel via atube 118 which runs from a pressurized hydrogen tank 114. The flow rateof hydrogen is controlled using an automated pressure-control valve 116which is disposed in tube 118 between the tank and fuel cell. If thestored hydrogen is released from the tank 114 by opening valve 116, itis consumed by fuel cell 112 to generate DC power. This DC power isintroduced into line 120 so that it is able to be consumed by thecontroller 110. Because a PLC uses AC power, the DC output of fuel cell112 must be converted. This is done by a power inverter 122 which islocated between controller 110 and line 120.

The entire control system 108 with its independent backup arrangementcomprising fuel cell 112 is able to be electronically isolated from DCbus 130 using a breaker 140 which is adapted (using controller 110) toopen up when voltage in the DC bus reaches a predetermined minimumvoltage.

FIG. 2 shows a fuel-control side 200 of the invention. The fuel controlsare housed in a cabinet 202 which is located on a platform 210. Platform210 may be a concrete slab or some other supporting surface.

A primary source of fuel is natural gas which is delivered in anunderground pipeline 204. A secondary source of natural gas ismaintained in a plurality of natural gas tanks 206. These tanks maintainnatural gas at high pressures and are all incorporated into a header208. Header 208 serves as a manifold which causes the pressure from eachof the tanks to be equalized.

A plurality of automated pressure-control valves (which in the preferredembodiment are explosion proof valves) are incorporated into the systemso that both (i) the underground primary utility source of natural gasfrom pipe 204 and (ii) stored source 206 can be used as fuel for themicroturbine 104 either alternatively or at the same time. Explosionproof valves are widely used in industry for controlling the flow ofnatural gas and other explosive gases. A primary pressure-control valve212 regulates the flow in a pipe 220 which receives natural gas fromunderground pipeline 204. A secondary pressure-control valve 214regulates the flow of gas in a pipe 222 which receives stored naturalgas from header 208. A third pressure-control valve 216 is disposed in apipe 226 and regulates the flow of natural gas to microturbine 104through underground turbine feeder pipe 224. Though explosion proofvalves have been selected for use in the preferred embodiment, otherkinds of flow-control valves, e.g., globe valves, could be used as welland still fall within the scope of the present invention.

Interposed between all three valves (212, 214, and 216) at a T-junctionbetween pipes 220, 222, and 226 is a surge tank. A surge tank is avessel which includes a chamber which receives gas from one or morefeeder pipes and is used to absorb pressure irregularities. Here it isused to minimize any disruptive effect caused by the automatedadjustments of valves 212 and 214. Otherwise manipulation of thesevalves might cause pressure irregularities in pipe 226 which could notbe accommodated by turbine 104. Turbines require the delivery of fuel onor about some specific pressure. For example, the turbine in thepreferred embodiment requires natural gas at 15 lbs. of pressure. Othersrequire 7 lbs. or some other constant pressure. Surge tank 218 alongwith pressure-control valve 216 maintain steady natural gas pressures inturbine feeder pipe 224 to ensure proper operation of the turbine.

Valves 212, 214, and 216 are all electronically controlled viaelectrical connections which are symbolically represented by dottedlines 230, 232, and 234 respectively in the figure. Each electricalconnection exists between the controller 110 (not visible in FIG. 2because it is contained in cabinet 202) and a respective valve. Themanner of electrical connection and programming required for controlpurposes are all within the skill of one skilled in the art. Connections230, 232, and 234 enable each of the pressure-control valves to beindividually controlled to regulate the flow rates and pressures inpipes 220, 222, and 226.

The overall objective is to, using pressure-control valves 212, 214,216, and surge tank 218, optionally and in variable amounts, use the twonatural gas sources while at the same time regulating the pressure inturbine feeder pipe 224 so that it is maintained at or close to theideal level, e.g., 15 lbs. of pressure. Valves 212 and 214 function toselect how much of each natural gas source (e.g., utility in pipe 204 orstored gas in tanks 206) is being consumed. Valve 216 is used tomaintain a steady pressure level in turbine feeder pipe 224 so that theturbine operates properly.

FIG. 3 shows the contents of control cabinet 202. Cabinet 202 includesfrom top to bottom, SMRs 134, inverter 122, and controller 110. Includedbelow are, from left to right, the LMPs 106, fuel cell 112, and hydrogentank 114. Some details have been omitted for simplicity sake, e.g., somecomponents as well as precise connection arrangements between all thedevices.

A power-management flow chart 400 of FIG. 4 shows both the operationalaspects of system 100 as well as different contingency plans intended tohandle natural gas availability problems. The entire power managementmethod is managed by a process which is programmed into controller 110.The FIG. 4 process assumes that valve 214 is initially closed but thatvalves 212 and 216 are opened up (at least partially).

In a first step 402 of the process, an inquiry is made as to whethernatural gas is available from the utility pipeline. This question isanswered by measuring the pressure in pipe 204 at valve 212 using apressure sensor (not shown). Information from this sensor is received bycontroller 110 through line of communications 232. Using controller 110,a determination is made as to whether this pressure is above apredetermined minimum value. The minimum value is set at or slightlyabove what is known as the minimum pressure required to drive theturbine. If the measured pressure is above this minimum, the processmoves on to a step 404.

In step 404, the surge tank will be supplied with natural gas via pipe204 only. To do so, pressure-control valve 212 is caused by thecontroller (through line of communications 232) to deliver natural gasat a pressure that is at or slightly above that required by the turbine(e.g., 15 lbs.). Valve 214 remains completely closed while this isoccuring.

After that, in step 405, controller 110 ensures that breaker 140 is inclosed position (if it is not already in that position). This isnecessary so that the controller receives power from the DC bus 130.

Next, in a step 406, the turbine generator consumes natural gas andgenerates AC power. The AC power is then converted to DC power by theSMRs 134. The DC power output from the SMRs 134 is introduced into DCbus 130 which maintains power to BTS 102. While this occurs, LMPs 106will charge in a step 408 because they are connected into the DC bus. Itis important that the LMPs 106 remain charged so that they are availablefor backup and bridging purposes if needed.

If in inquiry step 402 the pressure measured in pipe 204 at valve 212(using a pressure sensor) is detected to be below the predeterminedminimum pressure required to drive the turbine, the process moves on toa second inquiry step 410.

In step 410, an inquiry is made as to whether stored natural gas isavailable that, either alone or in combination with natural gasavailable from the utility, is sufficient to drive the turbine. Thecontroller determines the availability of stored natural gas in tanks206 by taking readings (through line of communications 232) from apressure sensor (not shown) in pipe 222 at valve 214. When thesereadings are received by controller 110, they are considered incombination with simultaneous pressure readings from pipe 204 regardingthe availability of utility natural gas and a determination is made bythe controller as to whether the total natural gas available will besufficient to meet the predetermined minimum value required to meet thefuel requirements of the turbine. If enough stored natural gas isavailable, the process moves on to a step 412.

In step 412 the necessary contribution of natural gas from the storagetanks 206 is introduced into surge tank 218. The controller accomplishesthis by opening up valve 214 to the extent necessary to meet the fuelrequirements of the turbine 104 based on all the available information.When this occurs, the stored natural gas mixes in surge tank 218 withwhatever utility natural gas is available (possibly none) and then, instep 406, causes the turbine to consume the natural gas from the twosources and drive a generator. The AC power produced is then convertedto DC and introduced into DC bus 130 to maintain power to the BTS.

Regardless of the mode of fuel consumption in step 406: (i) utilitynatural gas only, (ii) stored natural gas only, or (iii) a combinedsupply from both sources simultaneously, the process will continuallycheck in a step 414 to determine whether the total natural gas availableis sufficient to drive the turbine 104 and thus, meet the BTSrequirements for DC power consumption. This is done by measuring thepressure at valve 216 in pipe 226 using a pressure sensor. The readingfrom this sensor will be received by the controller via connection 234.The controller will compare this reading to a predetermined (and stored)value which represents the minimum pressure required to effectivelydrive turbine 104. If the measured value is above the minimum, theprocess will continuously loop between turbine consumption step 406 andchecking step 414 and the turbine will remain continuously operational.If, however, the supply of natural gas from both available sources isnot enough to power the turbine, the answer at step 414 will be no. Thiswill occur when: (i) there is a temporary dip in the power because ofsome fuel pressure irregularity, mechanical, or other momentary failure;or (ii) the turbine is completely nonfunctional because there is nolonger enough fuel to drive it. In either case, the process will move onto a step 416.

In step 416, an inquiry is made as to whether the LMPs have enoughcharge to maintain the BTS 102. This is determinable by measuring thevoltage in DC bus 130 using a voltage sensor (not shown). The controllerwill be programmed to recognize the minimum voltage which is indicativeof what will satisfy the minimum power required to support the BTS powerrequirements. If voltage is sensed at a level above the minimum, theLMPs 106 will drain in a step 418. For temporary dips in power, the LMPswill act to bridge, causing the momentary dip to have no effect on theactual power available to the DC bus 130. For substantial/longer lossesin power, the LMPs will act as a backup power source. Both scenarios arehandled by the FIG. 4 process.

After step 418, the process will continually loop back to step 402 andthen back through steps 410 and 416. This causes the process tocontinually monitor whether natural gas has become available from eitherof sources 204 or 206. If so, the turbine will be returned to service.If not, the LMPs 106 will continue to drain.

After a considerable amount of time without natural gas, the constantdependence on battery power will cause the charge in the batteries tobecome depleted. The controller 110 is programmed to recognize whenvoltage in the DC bus 130 drops to the point at which the BTS 102 isunable to function properly. When this occurs, the process causesbreaker 140 to be thrown in a step 420. This opens up the circuit,causing control system 108 including controller 110 and fuel cell 112 tobe electrically isolated from the DC bus 130.

At the same time breaker 140 is thrown, the controller also causespressure-control valve 116 to open up. This causes hydrogen to bedelivered from tank 114 to be consumed by the fuel cell to maintainpower to the controller 110 in a step 422. Thus, although power has beenlost to the BTS 102, control system 108 will remain functional becauseof the DC power produced by the hydrogen-powered fuel cell.

After step 422, the process loops back to step 402. This creates acontinuous loop which will cause the controller 110 to continuallymonitor whether natural gas has become available from either utilitysource 204 or storage tanks 206. If so, the turbine will come backonline and the process (pursuant to steps 402, 404, 405, and 406 orsteps 410, 412, 405, and 406) will cause the system to revert back to ACproduction and recharge the LMPs (in step 408). But if natural gas isstill not available, the fuel cell will continue to operate in step 424in order to keep the controller 110 powered.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, all matter shown in the accompanyingdrawings or described hereinabove is to be interpreted as illustrativeand not limiting. Accordingly, the scope of the present invention isdefined by the appended claims rather than the foregoing description.

1. A fuel-control system for regulating the administration of a firstfuel to a fuel consuming device, comprising: a system-controlling deviceadapted to consume a primary source of electrical power; said systemcontrolling device is also adapted to consume a secondary source ofelectrical power, said secondary source produced by noncombustiblyconsuming a second fuel.
 2. The system of claim 1 wherein said fuelconsuming device is a turbine.
 3. The system of claim 1 wherein saidfirst fuel is natural gas.
 4. The system of claim 1 wherein said secondfuel is hydrogen gas.
 5. The system of claim 1 wherein said secondarysource is derived from a fuel cell.
 6. The system of claim 1 comprising:a breaker which isolates said system controlling device and saidsecondary source from a circuit including said primary source when avoltage reading falls below a predetermined voltage level in saidcircuit.
 7. The system of claim 1 wherein said system-controlling deviceis a programmable logic controller.
 8. The system of claim 1 whereinsaid system-controlling computing device is a microprocessor.
 9. Thesystem of claim 1 wherein said system-controlling device is used tocontrol valves which regulate the administration of said first fuel tosaid fuel consuming device.
 10. The system of claim 8 wherein saidsystem-controlling device receives information from at least onepressure sensor, said sensor being located such that detects a first gaspressure in a first conduit.
 11. The system of claim 9 wherein saidsystem-controlling device manipulates said first pressure-control valvein response to said first gas pressure sensed in said first conduit. 12.A fuel-control system for a gas consuming device, said systemcomprising: a controller; a first source of a first gas received througha first conduit, said conduit leading into a chamber; a firstpressure-control valve in said first conduit; a first sensor at alocation in said first conduit, said first sensor reading informationregarding a first pressure, said information regarding said firstpressure being transmittable to said controller; a second source of asecond gas derived from a storage container through a second conduitinto said chamber; a second pressure-control valve in said secondconduit; and a second sensor at a location in said second conduit, saidsecond sensor reading information regarding a second pressure, saidinformation regarding said second pressure being transmittable to saidcontroller; said controller adapted to manipulate said first and secondpressure-control valves in response to said first and second readings tomaintain a steady pressure level in a third conduit, said third conduitrunning from said chamber to said gas consuming device.
 13. The systemof claim 12, comprising: a third pressure-control valve and a thirdsensor located in said third conduit, said third sensor readinginformation regarding a third pressure, said information regarding saidthird pressure being transmittable to said controller, said controlleradapted to manipulate said first, second, and third pressure-controlvalves in response to said first, second, and third readings to maintaina steady pressure level in a third conduit.
 14. The system of claim 12wherein said fuel consuming device is a turbine.
 15. The system of claim12 wherein said first and second gases are natural gas.
 16. The systemof claim 12 wherein said controller is one of a microprocessor and aprogrammable logic control device.
 17. The system of claim 12 where thecontroller is electrically coupled with a back up power system whichincludes a fuel cell.
 18. The system of claim 12 in which said chamberis a surge tank.
 19. A method of regulating the fuel flow into a gasturbine, said turbine receiving fuel through a feeder conduit from firstand second sources of gas, said first source derived from a pipeline,said second source being derived from a storage tank, said methodcomprising: providing a surge tank; delivering natural gas from saidfirst and second sources into said surge tank via first and secondconduits, respectively; delivering said natural gas from said surge tankto said turbine through said feeder conduit; incorporatingpressure-control valves and sensors into each of said first and secondconduits; measuring pressures in said first and second conduits usingsaid sensors; receiving said pressures measured into a controller; andusing said controller to manipulate said valves to supply said turbinewith fuel.
 20. The method of claim 19 comprising: providing a thirdvalve and a third sensor in said feeder line; receiving pressureinformation from said third sensor in said controller; using saidcontroller to manipulate said first, second, and third valves using saidinformation.